You can certainly call and have MS add it to your confirmation. The resort may or may not do anything special for the event- it depends on the CM's who are aware of it.
If you are planning a special meal for her, I'd make sure the staff at the restaurant is aware, as they would be more likely to acknowledge the birthday.
Housekeeping may create a towel sculpture, but otherwise the resort may not do anything to recognize the event. If you want something special to happen, you may want to make the arrangements yourself.
Then again... you never know what "magic" might occur!
Enjoy!